Relationship between Depression and Functional Measures in Overweight and Obese Persons with Osteoarthritis of the Knee

Osteoarthritis (OA) is the most common form of arthritis, affecting an estimated 21 million people in the United States in 1990 [1]. Depression is also highly prevalent in the United States, with 19 million people over the age of 18 years being affected by a depressive disorder in any given year [2]. In a recent longitudinal study of OA sufferers, 25.2 percent of 369 subjects met the criteria for depression [3-5].

The purpose of this study was to examine the relationship between depression and functional status of overweight and obese patients with OA of the knee. Our objectives were to (1) examine the prevalence of depressive symptoms in our sample; (2) examine the relationship between depressive symptoms, perceived physical function, and physical performance in overweight and obese adults with OA of the knee; and (3) determine what factors were associated with depressive symptoms. We hypothesized that (1) patients who reported more functional limitations would also report more depression, and (2) lower reported function will account for significant variance in depressive symptoms for this sample.

METHODS

Subject Selection

After the study was approved by the Human Studies Subcommittee, we recruited patients with documented OA of the knee from the General Medicine and Arthritis clinics at a midwestern Department of Veterans Affairs (VA) Hospital and the surrounding community. Patients were identified with International Classification of Diseases-9th Revision codes 715.06 or 715.26 as a primary or secondary diagnosis. Identified patients were sent a letter of invitation. To be contacted by the staff, the patient needed to respond positively to the letter of invitation by returning a stamped, self-addressed information sheet. We then invited patients for an initial visit in the laboratory and obtained written informed consent.

Inclusion Criteria

Patients 50 years or older with documented OA of the knee were invited to participate. We documented OA of the knee as radiographic findings of tibiofemoral joint changes of Grades 2 to 3 using the Kellgren-Lawrence criteria. Additionally, we included patients if their knee pain was symptomatically defined as mild to severe pain for most days of the week for at least 6 months before entry and if they were functional Class I to III of the American Rheumatology Association functional capacity criteria, had a body mass index (BMI) between 27 and 40 kg/[m.sup.2], and were able to attend scheduled exercise and nutrition counseling sessions.

Exclusion Criteria

Patients were excluded if they had undergone arthroscopic surgery of the knee within the previous 3 months; had severe back, hip, or ankle pain that prevented them from walking; or had joint replacements in both knees.

Description of Instruments

Center for Epidemiologic Studies Depression Scale

The Center for Epidemiologic Studies Depression Scale (CES-D) is a 20-item measure designed to evaluate symptoms of depression in the community population [6]. A score of [less than or equal to] 16 indicates that a person is not depressed, and a score of >16 indicates that a person is depressed. The CES-D has been shown to be reliable in general and patient populations, with internal consistency reported at 0.85 to 0.90 [6], and valid in patients with arthritis [7]. The CES-D has been successfully used in depression evaluation [6,8] and in normal and psychiatric populations and correlates with the clinical diagnosis of depression [6].

Western Ontario MacMaster

The Western Ontario and MacMaster Universities (Osteoarthritis Index) (WOMAC) Likert 3.1 questionnaire is designed to measure functional loss and pain in persons with arthritis [9-10]. In the difficulty domain, the focus is measuring tasks related to activities of daily living. The WOMAC is a disease-specific measure of factors affecting quality of life in persons with OA. …

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